Signaling system



July 12, 1932. w L, EDlsON 1,866,845

SIGNALING SYSTEM Filed NOV. 26, 1930 Patented July 12, 1932UNITEDQST'ATES PATENT OFFICE WILLIAM LESLIE EDISON, OF WILMINGTON,DELAWARE, ASSIGNOB TO THE W.'L. IHHSON I MANUFACTURINGCORPORATION, FWILMINGTON, DELAWARE, A CORPORATION OF DELAWAR SIGNALING SYSTEM"-Applicationflled November 26, 1930. Serial 110,498,281.

This invention relates toa high frequency alternating, current systemand more particularly to means for interconnecting the tubes of anamplifying system. The system herein disclosed is particularlyapplicable to the amplificationof radio signals, the inter:

connecting means being of a type. applicable to the radio amplificationstages, preventing oscillation due to mutual reaction.

It is the object of the present invention to provide an interconnectingarrangement for the tubes of an amplifying system, and a circuitincluding such arrangement which produces a high degree of amplificationwithout I oscillation, distortion or losses involved in resistancesuppression methods heretofore used in radio frequencyamplificationstages. The interconnecting arrangement specifically consists of a novelelement, the construction of which will be clear fromthe followingdescription read in conjunction with the accompanying drawing, in whichFig. 1 is a diagrammatic illustration of a portion of a circuitembodying the improved amplifying system; i

Fig. 2 is an elevation of the improved interconnecting element; and

Fig. 3 is a perspective view of apart of'the interconnecting element.

Referring first to Figs. Qand 3, the interconnecting element includes anordinary'tube 2 of insulating material on which is supported a coil 4.of insulated wire, closely or loosely wound depending upon theparticular impedance desired, the allowed distributed capacity, etc. Aclip 6 of elastic metal of the form'shown in Fig. 3 isadapted toclampthe coil and slide thereon as illustrated in Fig. 2, a lead 8 beingprovided for connecting the 40 slide conductively into a-circuit. Theclip 6 is separated from the convolutions of coil 4 by the insulationsthereon and therefore forms therewith a condenser, the capacity of whichdepends upon the area 'ofthe clip, the dielectric forming the coilinsulation, and the spacing and dimensions of the convolutions. Theelement, therefore, is,'to some extent, equivalent to a portion of acircuit including a condenser having a lead having variable metalliccontact by means of a slider clip, or I the like, with a coil. However,the novel element offers the advantages that no contact offeringlndeterminate resistance due to corrosion, pressure, etc. is interposedbetween the coil and condenser, and that shortened leads v are possiblebecause ofthe simpler arrangement.

The element also offers advantageous dynamic characteristics whenincorporated 1n a circuit in WlllCll high frequency oscillations exist.

For example, an amplifying circuit is illustrated in Fig. 1 includingthe improved elements in several places. In this circuit the coil L ofthe first element forms a tuned resonant circuit with a variablecondenser C the clip M of the first element being connected to theantenna A. One side of the condenser is connected to the grid of thefirst tube V shown in the present'instance as a screen grid, heater typetube arranged to be heated by alternating, current, although it may bereplaced by any other suitable type for amplifying purposes. thecondenser is grounded.

The plate of tube V is connected to the clip M of the second element,the coil L of which, together with variable condenser C forms a tunedresonant input circuit for tube The other side of movable plates of thecondensers C C C3 and C. on a common shaft.

When the proper constant voltages are applied to the plates, controlgrids and screen grids of the tubes in any of the ordinary fashions, thesystem will operate as an amplifier. The input circuit includes theresonantcircuit In -C coupled to the antenna capacity at H andaccordingly incoming signals impress high frequency voltage between thegrid and cathode of tube V The portion of L mutual to the antenna andresonant circuits may be varied by moving the clip along the coil, beingmaximum and equal to L when the clip is at the grid end of the coil andzero when the clip is at the grounded end.

In a similar fashion the variable com onents in the plate circuits ofthe various tu es produce variable grid potentials in the succeedingtubes through couplings M M and M Here also the mutual impedance may bevaried by sliding the clips along their respec tive coils. As a resultof the coupling, amplification takes place.

When suitable coils and condensers are used and the clips are properlyadjusted, it is found that very stable operation takes place with aminimum of distortion and without re sistance losses. Sharper selectionis also obtained. If the circuit tends to become unstable with change oftubes, readjustment of the clips will bring it back to equilibrium.

The improved interconnecting element has been illustrated in connectionwith the high frequency amplification stages only smce it is practicalonly in connection therewith. When the clip 6 is of small dimensions ofa range useful in practice, the capacity of the small condenser formedby it and the coil is so small that the impedance at low frequencieswould be very large. An arrangement offering the proper low impedancefor audio frequencies would have impractically large dimensions.

In the preferred modification disclosed, the clip is spaced from themetallic convolutions by reason of the fact they are insulated. If barewire is used for the coil, thespacings of convolutions being used toinsulate them from each other, a Clip may be used Which itself carriesspacing insulation in the form of enamel or the like. In some cases aninternal clip springing outwardly to conform to the inner surface of thecoil supporting tube could be used. However at high frequencies thedielectric hysteresis losses in this type of construction would beconsiderable.

What I claim and desire to protect by Letters Patent is:

1. An amplifying system including a thermionic tube having cathode, gridand plate elements, a grid circuit joining the grid and cathode of thetube, a coil in the grid circuit, and a conducting member spaced from,but closely adjacent to, convolutions of the coil,

said member being connected to a point the potential of which variesduring the operation of the system, the capacity between the member andcoil providing a low coupling impedance at radio frequencies.

2. An amplifying system including a thermionic tube having cathode, gridand plate elements, a grid circuit joining the grid and cathode of thetube, a coil, variations in voltage in which produce correspondingvariations in grid potential, and a conducting member spaced from, butclosely adjacent to, convolutions of the coil, said member beingconnected to a point the potential of which varies during the operationof the system, the capacity between the member and coil providing a lowcoupling impedance at radio frequencies.

3. An amplifying system including a thermionic tube having cathode, gridand plate elements, a grid circuit joining the grid and cathode of thetube, a coil in the grid circuit, and a conducting member spaced from,but closely adjacent to, convolutions of the coil, said member beingconnected to a point of varying potential extraneous to the gridcircuit, the capacity between the member and coil providing a lowcoupling impedance at radio frequencies.

4. An amplifying system including a thermionic tubes having cathode,grid and plate elements, a grid circuit joining the grid and cathode ofthe tube, a coil, variations in voltage in which produce correspondingvariatlons in grid potential. and a conducting member spaced from, butclosely adjacent to, convolutions of the coil, said member beingconnected to a point of varying potential extraneous to the gridcircuit, the capacity between the member and coil providing a lowcoupling impedance at radio frequencies.

5. An amplifying system including a thermionic tube having cathode, gridand plate elements, a tuned grid circuit joining the grid and cathode ofthe tube and including a coil and condenser, and a conducting memberspaced from, but closely adjacent to, convolutions of the coil, saidmember being connected to a point the potential of which varies duringthe operation of the system, the capacity between the member and coilproviding a low coupling impedance at radio frequencies.

6. An amplifying system including a thermionic tube having cathode, gridand plate elements. a grid circuit joining the grid and cathode of thetube, a coil in the grid circuit. and a conducting member spaced from,but closely adjacent to, convolutions of the coil,

and adjustable along the coil, said member being connected to a pointthe potential of which varies during the operation of the system, thecapacity between the member and coil providing a low coupling impedanceat radio frequencies.

7 An amplifying system including athermionic tube having cathode, gridand plate elements, a grid circuit joining the grid and cathode of thetube, a coil, variations in voltage in which produce correspondingvariations in grid potential, and a conducting member spaced from, butcloselyadjacent to, convolutions of the coil, and adjustable along thecoil, said member being connected to a point the potential ofwhichvaries during the operation of the system, the capacity between themember and coil providing a low coupling impedance at radio frequencies.

8. An amplifying system including a thermionic tube having cathode, gridand plate elements, a grid circuit joining the grid and cathode of thetube,a coil in the grid circuit, and a conducting member spaced from,but closely adjacent to, convolutions of the coil, and adjustable alongthe coil, saidmember being connected to a point of varying potentialextraneous to the grid circuit, the capacity between the member and coilproviding a low coupling impedance at radio frequencies. 9. Anamplifying system including a thermionic tube having cathode, grid andplate elements, a grid circuitjoining the grid and cathode of the tube,a coil, variations in voltage in which produce corresponding variationsin grid potential, and a conducting member spaced from, but closelyadjacent to, convolutions of the coil, and adjustable along the coil,said member being connected to a point of varying potential extraneousto the grid circuit, the capacity between the member and coil providinga low coupling impedance at radio frequencies.

10. An amplifying system including a thermionic tube having cathode,grid and plate elements, tuned grid circuit joining the grid and cathodeof the tube and including a coil and condenser, and a conducting memberspaced from, but closely adjacent to, 'convolutions of the coil, andadjustable along the coil, said member being connected to a pointthepotential of which varies during the operation of the system, thecapacity between the member and coil providing a low coupling impedanceat radio frequencies.

11. An amplifying system including a plurality of thermionic tubes eachof which has cathode, grid and plate elements, a plate circuit joiningthe plate and cathode of one tube, a grid circuit joining the grid andcathode of a succeeding tube, a coil, variation in voltage in whichproduce corresponding variations in the potential of the grid of thesucceeding tube, and a conducting member spaced from, but closelyadjacent to, convolutions of the coil, said member being connected tosaid plate circuit, the capacity between the member and coil providing alow coupling impedance at radio frequencies.

12. An amplifying system including a plurality of thermionic tubes eachof which has cathode, grid and plate elements, a plate circuit joiningthe plate and cathode of one tube, a grid circuit joining the grid andcathode of a succeeding tube, a coil, variation in voltage quencies.

13. An amplifying system including avplurality of thermionic tubes eachof which has cathode, grid and plate elements, a plate circuit joiningthe plate and cathode of one tube, a grid circuit joining the grid andcathode of a succeeding tube, a coil, variation in voltage in whichproduce corresponding variations in the potential of the grid of thesucceeding tube, and a conducting member spaced from, but closelyadjacent to, convolutions of the coil, said member being connected sothat variations in potential are produced therein corresponding tovariations in potential of the plate of the preceding tube, the capacitybetween the member and coil providing a low coupling impedance at radiofrequencies.

14. An amplifying system including a plurality of thermionic tubes eachof which has cathode, grid and plate elements, a plate circuit oiningthe plate and cathode of one tube, a grid circuit joining the grid andcathode of a succeeding tube, a coil, variation in voltage in whichproduce corresponding variations in the potential of the grid of thesucceeding tube, and a conducting member spaced from, but closelyadjacent to, convolutions of the coil, and adjustable along the coil,said member being connected to said plate circuit, the capacity betweenthe member and coil providing a low coupling impedance at radiofrequencies.

15. An amplifying system including a plurality of thermionic tubes eachof which has cathode, grid and plate elements, a plate circuit joiningthe plate and cathode of one tube, a grid circuit oining the grid andcathode of a succeeding tube, a coil, variation in voltage in whichproduce corresponding variations in the potential of the grid of thesucceeding tube, and a conducting member spaced from, but closelyadjacent to, convolutions of the coil, and adjustable along the coil,said member being connected to the plate of the preceding tube so as tobe at substantially the same potential as the plate, the capacitybetween'the member and coil providing a low coupling impedance at radiofrequencies.

16. An amplifying system including a plurality of thermionic tubes eachof which has cathode, grid and plate elements, a plate circuit joiningthe plate and cathode of one tube,

4 means a grid cineuit-qjeining the grid and cathode ,ofarsueceedingtube, a coil, variation in voltage in which produce correspondingvariations in the potential of the grid of the succeeding tube, and aconducting member spaced from, but closely adjacent to, convolutions ofthe coil, and adjustable along the coil, .said member being connected sothat Variations in potential are produced therein corresponding tovariations in potential of the plate of the preceding tube, the capacitybetween the member and coil providing .a low coupling impedance atradiofrequencies.

In testimony of which invention I have hereunto set my hand atWVilmington, Dela- Ware, on this 24th day of November, 1930.

WILLIAM LESLIE EDISON.

